Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 220554 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1254 AM EST Thu Feb 22 2018 .SYNOPSIS... High pressure will remain off the Southeast coast, which will keep well above normal temperatures through the remainder of this week. Chances of rain should increase as a cold front approaches from the west. This front should cross overhead later in the weekend. && .NEAR TERM /THROUGH TODAY/...
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As of 1245 AM EST Thursday... Latest models indicate that wedge will be slower to arrive than earlier anticipated. It may not get past LYH until after sunset Thursday, then surge southwest into Friday morning. Have reduced pops based on latest high res models with respect to wedge and holding rain off from western front with that activity reaching the Alleghany front and not likely much further east. Movement of rain may be more north along backdoor front and across northern VA/WV. For now, temps and dewpoints were running close to advertised values with few changes needed. Changes were mainly with pops through Thursday afternoon. As of 230 PM EST Wednesday... An anomalous upper level ridge remains off the Southeast coast, which is providing quite a warm day for February with near record high temperatures expected. See the climate section for more details. Cloud cover has been thinning over most of the area during the day, but a copious amount remains over the southern Blue Ridge. It will likely not break up until late afternoon. The latest mesoscale models are not impressive with the development of a few showers or thunderstorms along and west of the Blue Ridge, but only a slight trim to coverage and POPs was made as enough warming is taking place to provide some weak instability. For this evening and beyond in this period due to what happens tomorrow, this forecast steered away from the GFS solution and in more agreement with the NAM and higher- resolution models. It will remain unseasonably mild overnight, but a cold front will approach from the west to possibly bring a few showers. Coverage appears highest over the southern Blue Ridge and parts of the Alleghany Highlands of Virginia. Meanwhile, high pressure will head east of the Great Lakes and begin to wedge southward along the eastern slopes of the Appalachian Mountains. As a result, a backdoor cold front should slide southward east of the Blue Ridge toward Thursday morning. Several adjustments were made for Thursday such as shaping temperatures to fall throughout the day in the Piedmont along with adding areas of fog and drizzle. POPs were also increased near Lynchburg to accommodate the likelihood of rain developing along the backdoor cold front. Temperatures were also shoved well below guidance, and the timing of the wedge was also sped up a few hours based on the latest high-resolution model solutions.
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&& .SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/... As of 200 PM EST Wednesday... Surface front will continue to bow south through much of the region Thursday night per the favored colder Nam before slowly lifting back north Friday ahead of another stronger wave lifting by well to northwest. This would support higher pops over the north closer to the baroclinic zone aloft and perhaps spotty light rain/drizzle behind the boundary into early Friday. Models suggest only weak support for added measurable rainfall Friday afternoon as the main lift passes well west and the wedge lingers for much of the day. Will keep some low pops going mainly north/west with perhaps lingering drizzle elsewhere Friday. Temps into Friday very tricky pending exactly where the backdoor front ends up as latest Mos showing a 10-15 degree difference in values from the colder Nam to the warmer GFS. For now will lean more toward the Nam but stay above its coldest values at this point. Front should lift back to the north Friday night into Saturday ahead of stronger shortwave energy heading northeast out of the central states. This will gradually push the area back into the warm sector Saturday into Saturday night. However lift and deeper moisture will remain north and west of the area until the moisture ahead of the front arrives west late Saturday night. Appears could be some scattering of showers mainly north and west, but overall chance to slight pops which may be overdone until very late Saturday night. Lows Friday night remain iffy with lows mostly 40s to mid 50s with values steadying/rising late. Highs Saturday look to be mostly late day within the residual eastern wedge while perhaps jumping to around 70 west espcly if more sunshine occurs. Thus stayed below guidance given the likely slower trend of Cad erosion at this point. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... As of 145 PM EST Wednesday... Strong upper ridge off the southeast coast looks to weaken during the period allowing more in the way of zonal flow to take shape next week. This will initially occur as stronger shortwave energy passes well north late in the weekend with a trailing cold front crossing the area from the west on Sunday per model consensus. Swath of weakening showers along the boundary should affect the region during the day although some solutions remain slower and have much of the rain behind the front which would suggest best pops west at this this point. Showers may also linger far southern sections Sunday evening as the boundary folds over otherwise drier later Sunday night across the region. Should be the last day of much above normal highs with another round of 60s to lower 70s. Drier/cooler air follows the front for early next week as high pressure builds in Monday and wedges in from the north on Tuesday. This likely to return some clouds to the region by later Tuesday with the wedge holding into Wednesday. May see another weak shortwave pass along the boundary just to our south Monday night per 00z Euro which could bring more rain back to southern sections but iffy. Otherwise next impulse dropping out of the Rockies may tag with the front to bring another area of organized rainfall into the region by later Wednesday. Temps cooler into next week, but still above normal with highs 50s to lower 60s. && .AVIATION /06Z THURSDAY THROUGH MONDAY/...
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As of 1245 PM EST Wednesday... A strong subtropical ridge remains anchored off the southeast U.S. coast providing our forecast area with unseasonably warm temperatures, southwest flow, and pseudo summerlike conditions. Meanwhile, a weak cold front was approaching from the west, but will make little additional progress eastward thanks to the strong upper ridge. However, the front will be close enough during the next 24 hours combined with a weak disturbance tracking around the northwest side of the upper ridge and an approaching back door front from the northeast Thursday to generate scattered showers overnight mainly across southeast WV. As the backdoor front arrives from the northeast Thursday afternoon, about six hours slower than previously anticipated, low clouds, drizzle, and MVFR BR will likely develop in its wake. It may be until after sunset before it surges southward, namely Thursday evening. The wedge will maximize in intensity and areal coverage around daybreak Friday, then begin to retreat northward Friday afternoon. Overall at the current time we are seeing mostly MVFR ceilings with scattered mid and high clouds. Ceilings will lower from the northeast overnight even in advance of the wedge, leaving most areas with a persistent low cloud deck Thursday morning, becoming BKN mid day with largely MVFR or worse ceilings through about 15Z, then MVFR to low end VFR. Drizzle will also be possible especially near the Blue Ridge and through the New River and Roanoke River Valleys. The drizzle and fog will contribute to periods of MVFR- IFR visibilities after midnight Thursday and off and on, at least through the morning Friday in most areas. Despite the abundance of high clouds, KLWB has managed to see radiational fog develop and has become LIFR with 1/4SM FG VV001. This will likely be in/out during the night with little to change this synoptically, unless some of the mid clouds and showers to the west can reach the area later, so will have slight improvement in conditions there after 09Z. Winds in advance of the wedge will be S-SW 5-10 mph becoming variable or light northeast behind the wedge on late Thursday/Thursday night. Medium confidence in ceilings and visibilities through the TAF valid period. Medium to high confidence in wind direction and speed through 12Z. Extended Aviation Discussion... Conditions will likely plummet to IFR by Friday morning and likely remain IFR to MVFR throughout the day. Eventually, the backdoor cold front will stall along the Virginia and North Carolina line and retreat northward as a warm front toward Friday evening. VFR conditions should return for most locations during Friday night and Saturday aside from any typical low clouds along the Blue Ridge on Saturday morning. By Saturday afternoon, shower coverage should increase as a cold front arrives from the west that could bring MVFR/IFR conditions toward Sunday. Better flying weather should return later on Monday.
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&& .CLIMATE... As of 700 PM EST Wednesday... Several record high maximum temperatures were set today. These include 77 degrees at Roanoke, 79 degrees at Danville, 76 degrees at Lynchburg, 73 degrees at Blacksburg, and 74 degrees at Bluefield. The previous records for these sites and dates are listed below: Wednesday 2/21/2018 Site MaxT Year HiMin Year BLF 65 1996 54 1997 DAN 75 2011 55 1953 LYH 75 1930 50 1981 ROA 73 1930 48 1997 RNK 71 1986 49 1953 Below are the all-time warmest minimum temperatures recorded during the month of February, for our five climate sites with long-established periods of record: Today`s readings will be updated after midnight. Warmest HiMin - February: Site HiMin Date BLF 57 Feb 5 2008 DAN 60 Feb 18 2008 LYH 59 Feb 20 1939 ROA 57 Feb 12 1932 RNK 52 Feb 16 1990 && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...PW NEAR TERM...PW SHORT TERM...JH LONG TERM...JH AVIATION...PW/RAB CLIMATE...AL

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